Fix TAP tests to use only standard command-line argument ordering.

Some of the TAP tests were supposing that PG programs would accept switches
after non-switch arguments on their command lines.  While GNU getopt_long()
does allow that, our own implementation does not, and it's nowhere
suggested in our documentation that such cases should work.  Adjust the
tests to use only the documented syntax.

Back-patch to 9.4, since without this the TAP tests fail when run with
src/port's getopt_long() implementation.

Michael Paquier